Analysis of Vitamin C (ascorbic acid) Contents packed fruit juice by UV-spectrophotometry and Redox Titration Methods

Abstract

Total vitamin C (ascorbic acid + dehydroascorbic acid) has been determined by UV-spectrophotometric method in various fruit juices. In this method, a blended sample is homogenized with 3% metaphosphoric acid-10% acetic acid solu'an. Then addition of bromine water oxidizes ascorbic acid to dehydroascorbic acid in presence of acetic acid and the excess of bromine is removed by a few drops of 10% thiourea. After coupling with 2,4-dinitrophenyl hydrazine at 37°C temperature for three hours, the solution is cooled in an ice bath and is treated with chilled 85% H2SO4 to produce a red colour complex and the absorbance is measured spectrophotometrically at 521 nm. This method obeyed Beer's law as was tested by using a standard ascorbic acid. Also ascorbic acid can be determined by redox titration. We performed an iodimetric back-titration in which we generated a measured excess of iodine in the sample solution and then we titrated the unreacted iodine with a standard sodium thiosulfate solution. Our purpose is to determine the Vitamin C content in some packed (industrial) fruit juices and compare the values with that labeled on the packed fruit juices. The samples were collected from different markets in Benghazi.Such as Rhyhan, Mazraa, Judi, Alhanaa, Nadic, Viva, Rani, Bravo, Suntop, and Stantal of different kinds.